[98 



III RKDtTV AND EVOLUTION IN PLANTS 



lower California, was a saline area of a so pronounced 

 desert type that its flora contained less than 140 species 

 of ferns and flowerng plants, five of which were endemic. 

 During the winter of 1904-1905 the fresh waters of the 

 Colorado River began to debouche into this basin, and 

 by early 1907 had formed a brackish lake, over 80 feet deep 

 and of about 450 square miles in area, known as the Salton 

 Sea. At the end of ten years it still had an area of some- 

 what less than 300 square miles. Some three or four 

 hundred -years previously the entire Salton Basin was 



FIG. 85. Sketch map showing the geographical distribution of the sun- 

 dew, Droscra fdiformh. (After M. L. Fernald.) 



occupied with a lake of over 2,000 square miles in area, 

 which, in turn, had dried up and given place to the desert 

 conditions above mentioned. It is not improbable that 

 such drastic changes as this may have resulted in the 

 obliteration of one or more species, though the flora was 

 not well enough known previous to the last inundation 

 to make a definite statement on this point possible. For 

 example, the presence there of endemic species was not 

 known until the recent botanical survey of the region 

 lying between the late water level and that of the ancient 



